Objective lens



United States Patent OBJECTIVE LENS John D. Hayes, Rochester, and LenaM. Hudson, Brighton, N.Y., assignors to Bausch & Lomb Optical Company,Rochester, N.Y., a corporation of New York Filed Apr. 25, 1958, Ser. No.730,909

3 Claims. (CI. 88-57) This invention relates to photographic andtelevision lens systems and the like having large relative apertures andmoderate angular fields and it particularly relates to improvements inthose optical objectives which are usually classified as modifiedtriplets.

Such photographic objectives having the positive-negative-positiveconstruction herein disclosed comprise a front positive lens group whichconsists of three single air-spaced meniscus lenses, each of which haspositive power. Comparatively large relative apertures at least as greatas f/.1.1 may be obtained in the triplet type of objectives in this waywhile maintaining a high quality of image aberrations such as sphericaland chromatic aberrations, astigmatism, coma, sine condition, distortionand field curvature.

It is an object of this invention to provide a photographic objective orthe like of the above-described form having a large relative apertureand a high degree of correction of all the above-mentioned imageaberrations and further provide an objective which may be manufacturedby the most economical procedures and processes. Further objects andadvantages will be apparent by reference to the following specificationand the accompanying drawing, wherein:

Fig. 1 is a diagrammatic view of a preferred form of our invention;

Figs. 2 and 3 are tables of numerical constructional data describingExamples I and II, respectively, which are two successful forms of ourinvention;

Fig. 4 is a graphical representation of the residual sphericalaberration for image rays in the D and G portion of the spectrum asrelated to the form of lens system shown in Example I of Fig. 2, and

Fig. 5 is a graphical representation of the sagittal and tangentialastigmatism designated by S and T, respectively, and related to ExampleI of Fig. 2.

With reference to Fig. 1 of the drawing, the preferred lens systemcomprises a group of three single air-spaced meniscus lenses A, B and Cof positive power in optical alignment with each other and located onthe long conjugate or front side of said system, said lenses all beingconvex toward the front. Spaced rearwardly thereof is a. singleplane-concave lens D of negative power which is coaxially alignedbetween the group of lenses A, B and C on the front side and anair-spaced double convex single lens E on the rear side. In the spacebetween lenses D and E, a diaphragm is located.

According to our invention, the purpose of the aforesaid group ofpositive meniscus lenses A, B and C is to provide an abnormally largerelative aperture of at least 3/ 1.1 for said system and this result isachieved by determining the most advantageous ratio of the power of eachsuch lens to the other lenses in the group and by determining the bestratios of power of lenses D and E to the sum of the individualcollective powers of lenses A, B and C of said group. In accordance withour computations and experiments, the best values for the power of theindividual lenses A, B, C, D and E for one successful form of ourinvention was determined to be as stated herebelow for Example I:

Lens: Power (diopters) +4.514 B +2344 C +9306 D -22.697 E +15.427

The corresponding powers of the lenses A to E inclusive as found in asecond successful form of our invention for Example II are as statedherebelow:

Lens: Power (diopters) A +4.7183 B +2.4449 C +9.3666 D -22.73 16 E15.1303

The aforementioned ratio between the stated powers of the A, B and Clenses within said lens group in Example I are:

-1.9300 and PA where P denotes the power of the lens. The correspondingratios between the stated powers of the A, B and C lenses in Example Hare:

& P.

=1.929s and %=1.9s53

P =1.4041 (P H -l-P For Example H- In general, we have produced superiorobjectives of the above-described type by choosing constructional andperformance data within the limiting values stated herebelow:

P. 1.9 to 2.0

P =1.35 to 1.45 (P +P +P P =.90 to .98 (P i-P -H n for D lens=1.7200 to1.7650 v for D lens =26.0 to 30.0 S =6.0 to 10.0 (S -PS S +S =2.5 to 4.0(S +S +S rection of image aberrations is also excellent. This fact isparticularly well evidenced by reference to the graphs shown in Figs. 4and of the drawing. Curves D and G of Fig. 4 show the superiorcorrection of the spherical 4 We claim: '1. A lens system of the kinddescribed which is corrected for spherical and chromatic aberrations,astigmatism, coma, sine condition, distortion and field curvatureaberrations for light in the D and G portion of the 5 and consists offive single air-spaced lenses which are visible spectrum within amoderate angular field of 30. optically aligned with each other, thefirst three lenses The solid line curve S and the dotted line curve T ofon the long conjugate side of said system being collective Fig. 5representing the sagittal and tangential astigmameniscus lenses, thefourth lens being a dispersive lens, tism, respectively, for the sameangular field further and the rearmost lens being a collective lens, therefracshow the excellent performance qualities of the above tivecurvatures of said lenses being given by the followdescribed objective.ing mathematical expressions in which R, to R repre- Two specificexamples numbered I and H of our insent said curvatures numbered fromthe front toward vention are shown in Figs. 2 and 3, respectively, inthe the rear of the system and F represents the equivalent drawings andthe constructional data therefor is duplifocus of said system; catedherebelow: 0.9 F R1 L0 F Example I 2.7 F R, 3.0 F [E.F.=100 B.F.=40.62 11.1 r.a.-so.1 0.8 F R 1.0 F 1.1 F R l.5 F Lens curvatures ThicknessSpaces m, r ,45 F R ,5 5 F R 1.5 F R 1.7 F 1 -9430 R7 2.0 F A .3 F R .4F

R: m2 .8 F R, 1.0 F B T,=1o.ss 1.6570 51.2 -7 F Rm -9F 5:=0.38 the axiallens thicknesses being given by the following 0 13,1716 380 w 5mathematical expressions wherein T to T represent said R6 2 B 676thicknesses numbered from the front toward the rear of R, :ee thesystem; D T4=2.69 1.7506 27.8 .15 F T1 ,16F 8,1192 .10 F T .11 F R. 9223.17 F T .20 F 2. 12-1816 1.6700 41.2 112 F 4 F RIF-7538 .17 F T .20 F

35 Example H the air spaces between said components being g1ven by thefollowing mathematlcal expressions and being desiglay-3956 flu nated bythe letters S to S numbering from the front toward the rear of saidsystem; Lens Curvatures Thickness Spaces n. v

40 .003 F S .0O5 F R; =91.41 2 F A. T|=l5.13 1.6200 60.3 ,04 F S3 08 Fst=0.3s .16 F s, .19 F B 46-40 TF1, mm m 5 F R=125'96 83:038 2. Aphotographic objective corrected for spherical Rs=50.53 and chromaticaberrations, astigmatism, coma, sine con- 0 36816656 TF1, 5&5 dition,distortion and field curvature consisting of five 51-5122 air-spacedsingle lenses in optical alignment with each D TF2 506 218 other andconstructed according to the constructional Rt =33.02 84:1) data givenherebelow: R. =92. s=4.e0 [E.F.-100 B.F.-4o.62 11 F.A.=30.] ETt=1s.74 1. 6700 47.2

Rm=-78.34 Lens Ourvatures Thickness Spaces m, r

55 wherein A, B, c, D and E designate the individual lenses, A R1 TF1,1,6200 R to R inclusive designate the lens curvatures, T to 1 =282e38 Tinclusive designate the lens thicknesses, S to S inclusive designate theair spaces between the lenses, all of B 135 38 Tl=loe53 which arenumbered from the front, n denotes the re- 60 s,= fractive index for theD line of the spectrum of the glass 0 R5 T 76 1 6380 55 5 from which thelenses are made, and v denotes the dis- R. =166.92 persion or Abbenumber for said glass. R =6, 51:6

Although only two embodiments of our invention have D 1 T|=2.69 1.750627.8 been shown and described in detail, it will be under- 65 R633 8:1792 stood that other embodiments may be constructed within Si=4 61 theconstructional limits hereinbefore stated. In all E 13:18 76 1 6700 47 2forms of this invention, only single lenses are provided Rm=75.38

having mostly low curvatures and moderate thickness and said lensesbeing made from easily obtainable glasses so as to provide at very lowcost a lens system having wherein R to R inclusive designate the lenscurvatures, relative apertures at least as great as f/'l.l and having Tto T inclusive designate the lens thicknesses, S to S superiorcorrection for the aforementioned image aberrainclusive designate thespaces between the lenses, n tions, all of which is in accordance withthe objects of designates the refractive index of the glass for the Dline this invention. of the spectrum for the respective lenses and vdesignates the Abbe number of said lenses numbering from the front tothe rear of said system.

3. A photographic objective corrected for spherical and chromaticaberrations, astigmatism, coma, sine condition, distortion and fieldcurvature consisting of five air-spaced single lenses in opticalalignment with each other and constructed according to theconstructional data given herebelow:

[E.F.-100 B.F.=39.56 //1.1 F.A.-30.1

Lens Curvatures Thickness Spaces m, v

R; =9L47 A 'l =15.13 1. 6200 60.3

S1=0.38 Rs =86.40 B 13:10.52 1.6110 58.8

Sz=0.38 Rs 50.53 C 13:19.27 1.6380 65.5

81-522 R1 IQ D P -2.68 1. 7506 27.8

8 -1730 S|=4.60 R. =92.08 E T|-18.74 1. 6700 47.2

wherein R to R inclusive designate the lens curvatures, T to T inclusivedesignate the lens thicknesses, S to S inclusive designate the spacesbetween the lenses, n designates the refractive index of the glass forthe D line of the spectrum for the respective lenses and v designatesthe Abbe number of said lenses numbering from the front to the rear ofsaid system.

References Cited in the file of this patent UNITED STATES PATENTS1,540,752 Bielicke June 9, 1925 2,346,061 Altman Apr. 4, 1944 2,576,436Baker Nov. 27, 1951 2,586,866 Schade Feb. 26, 1952 2,767,614 Altman Oct.23, 1956 2,821,112 Lautenbacher et al. Jan. 28, 1958 2,861,500 TronnierNov. 25, 1958 FOREIGN PATENTS 428,657 Germany May 10,1926

UNITED STATES PATENT QFFICE CERTIFICATE Q CORRECTIGN Patent N0o2,949,821 August 28 1960 Column 1, line 25, for "f/elol'" read f/l.l

Signed and sealed this 4th day of April 1961.,

ggge ERNEST W. SWIDER X ARTHUR w. CROCKER Attesting Oflicer ctmgCommissioner-0f Patents

